When I set this first, all is OK, and both servers announce the external routes (VIPs) out with a "Forwarding address" of *Router ID* However, while by testing the failover of the interfaces per server by shutting down one interface and keeping the other interface one is UP,the external OSPF route is advertised by the dns servers with forwarding address of the physical interface ,since the interface is down the next hop IP is not valid and hence all the traffic destined to this VIP will be blackhole.By restarting NIC interfaces"service network restart" the scenario becomes normal and the forward address getting the router ID. Can you assist us why this scenario happed on quagga and not in zebra.